An NHS chief who spoke out against the Government's controversial Health Bill last night claimed he had been the target of political "smears" by Andrew Lansley's department.

Professor John Ashton, the head of public health in Cumbria, who was awarded a CBE for services to the NHS, claimed that someone on behalf of the Health Secretary called his local BBC radio station to allege that he could not speak objectively because he was a member of the Labour Party.

The 64-year-old said he had been a member since he was 17, but it was an "outrageous smear" to suggest this clouded his independence as a doctor.

Professor Ashton had had a warning from his Primary Care Trust last week threatening him with disciplinary action for co-signing a letter to The Independent criticising the health reforms. When BBC Radio Cumbria covered the story, someone from Conservative Party HQ called the station to point out that the doctor was an active Labour Party member. The professor said he had worked closely with politicians from all parties and was a critic of the last Labour government.

He added: "The fact that I am a member of the Labour Party has never interfered with my professional objectivity. For me, being a member of the Labour Party is like being Church of England, or black or gay. It is where my values come from. It is the fundamental right of citizenship to belong to a political party."

A Conservative Party spokesman said: "The BBC has a responsibility to report news objectively. They should always inform their viewers if the person they are interviewing has political motives, and it is absolutely appropriate for us to request that they do so."